Custom Alert Rule Builder for Contract Events

WHAT IT DOES

Custom Alert Rule Builder for Contract Events lets you define precise event monitoring rules for any EVM contract. You provide a contract address, its ABI, a block range, and optional topic filters, and the tool scans the chain for matching events. It decodes each event using the ABI you supplied, displaying the event name, parameter values, transaction hash, and block number in a clean, readable format. You can set up alerts for specific event types—like Transfer, Approval, OwnershipTransferred, or custom events—and filter by indexed parameters to reduce noise. The tool automatically handles RPC limitations by chunking block ranges and backing off when providers refuse large queries. It shows progress as it scans, and summarizes how many events were found, how many logs were decoded, and how many unrecognized logs were skipped. This is essential for monitoring contract activity, detecting suspicious transactions, tracking protocol events, or building custom notification systems for DeFi positions, NFT sales, governance proposals, or any on-chain activity that emits events.

HOW TO USE

Connect your wallet or use the connected provider to access the EVM network. Enter the contract address you want to monitor. Paste the contract's ABI as a JSON array—this tells the tool how to decode the events. Specify the block range you want to scan: enter a starting block number and an ending block number (or use "latest" to scan up to the current block). Optionally, you can add topic filters to only scan for events with specific indexed parameters—for example, to only see Transfer events involving a particular address. Click "Scan for Events." The tool fetches logs in chunks, automatically handling RPC errors by halving the chunk size and retrying. Once complete, it displays each decoded event with its name, parameters, transaction hash, and block number. You can use this to set up recurring scans, build alert systems, or simply audit contract activity over time.

THE REAL MECHANISM

The tool uses the Ethereum JSON-RPC eth_getLogs method with a filter object containing the contract address, block range, and optional topics. Since public RPCs often cap the number of blocks eth_getLogs can scan in a single request, the tool implements an intelligent chunking algorithm (PLAYBOOK-C §5.1): it walks backward through the requested block range in chunks. If a request fails, it halves the chunk size and retries the same range, continuing until successful or until the chunk becomes too small. This prevents the scan from failing entirely when hitting a provider's limit. The tool then passes each log through the ethers.js Interface parser using the ABI you provided. The Interface object is built once from the ABI, and parseLog is called on each log. If parsing succeeds, the tool extracts the event name, signature, and indexed/non-indexed parameter values, displaying them in a structured format. For failures, the tool counts unrecognized logs but does not crash. All scanning is done client-side with no external dependencies beyond the RPC provider.

WHAT IT CANNOT SEE

This tool cannot monitor events in real-time—every scan is a manual query and must be re-run to see new events. It cannot scan more than 10,000 blocks per query due to RPC limits and timeout constraints. It cannot detect events that were emitted before the contract was deployed, as those logs do not exist on-chain. It cannot decode events without a valid ABI—if your ABI is incorrect or incomplete, some logs will show as unrecognized. It cannot alert on internal transactions, state changes, or any on-chain activity that does not emit a log. It cannot detect events from proxy contracts unless you point it at the implementation address or the proxy emits events itself. It cannot scan across multiple contracts in a single query. It cannot detect events that were emitted but are no longer available due to chain pruning on some networks. It cannot verify that the provided ABI matches the actual deployed contract—you are responsible for supplying the correct interface.

PLEASE NOTE

Custom Alert Rule Builder for Contract Events works exclusively with Ethereum Virtual Machine (EVM) compatible chains including Ethereum, Goerli, Sepolia, Polygon, BSC, Arbitrum, Optimism, Avalanche, and others. The tool requires the contract address to be valid on the selected network and for the RPC node to support eth_getLogs. It reads data only and does not send any transactions or modifications to the blockchain. All processing occurs client-side in your browser; no data is sent to any external server. The tool is free to use and does not require authentication. For optimal performance, keep block ranges under 10,000 blocks and use topic filters to narrow results.